JPH04327758A - Hot water feeder - Google Patents

Abstract

PURPOSE:To enable a fast stabilization of hot water feeding temperature to be attained by a method wherein when a flow rate is rapidly changed, an FF control is carried out without carrying out an FB control, when a flow rate is rapidly decreased, the FF volume is reduced less than a calculated FF volume and when a flow rate is rapidly increased, the FF volume is increased more than the calculated FF volume and then an over-shoot and an under-shoot are eliminated within a quite short period of time in response to an initial time of variation of the flow rate. CONSTITUTION:A hot water feeder is comprised of a combustion amount calculation circuit 31, a proportional integration circuit 32, a combustion amount correction circuit 33, a proportional integration amount correction circuit 34 and a flow rate variation sensing circuit 35. In addition, the hot water feeder is made such that a combustion amount calculation varying circuit 36 for performing addition, subtraction, multiplication and division only for a rate of flow rate variation or a specified rate is disposed between the combustion volume calculation circuit 31 and the combustion volume correction circuit 33 or a hot water temperature control device 11 having a timer circuit 37 is disposed between the flow rate variation sensing circuit 35 and the combustion volume calculation varying circuit 36.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water heater that has good responsiveness and can quickly stabilize the temperature of hot water when the flow rate changes rapidly.

0002

[Background Art] Conventionally, in water heaters, when the flow rate changes suddenly, the hot water temperature may temporarily go above or below the set temperature, making it unstable.Technology has been developed to solve this problem. is disclosed in Japanese Patent Application Laid-Open No. 58-79928, but this has poor responsiveness because it responds to changes in outlet temperature. In other words, this is always FF
Since control and FB control (PID control) are used together,
Since PID control is performed even when the flow rate changes rapidly, the integral term at the time of overshoot accumulates rapidly, causing undershoot.

[0003] Therefore, as a solution to this drawback of poor responsiveness, a water heater that prevents deterioration of the hot water supply characteristics caused by changes in flow rate with good responsiveness is proposed.
It is disclosed in Japanese Patent No. 5081. As shown in FIG. 3, this water heater is equipped with a hot water control device configured as follows. That is, it includes an outlet hot water temperature detection circuit 40, an input water amount detection circuit 41, an input water temperature detection circuit 42, a temperature setting circuit 43, a combustion amount calculation circuit 44, a proportional integral circuit 45, and a combustion amount correction circuit 46, and further includes the water input amount detection circuit. 41 and the proportional integral circuit 45, there are provided a water inflow amount change detection circuit 47 that detects sudden changes in the amount of water inflow, and an integral amount cancel circuit 48 that removes unnecessary integral amounts.

0004

[Problems to be Solved by the Invention] Among the above-mentioned conventional techniques, the known technique disclosed in Japanese Utility Model Publication No. 2-25081 is provided with a water inflow amount change detection circuit 47 and an integral amount canceling circuit 48 for removing unnecessary integral amounts. Stable hot water discharge characteristics are obtained by detecting sudden changes in the water input amount and removing unnecessary integral amounts, and the response is relatively good. However, when the flow rate changes suddenly, P control or Since PD control is performed, there is a delay at the initial stage of flow rate change, so overshoot cannot be improved and undershoot cannot be completely eliminated.

[0005]

[Means for Solving the Problems] In view of the above-mentioned state of the prior art, the present invention does not perform FB control when the flow rate changes rapidly, and when the flow rate drastically decreases, the FF amount is made smaller than the calculated FF amount. Also, when the flow rate increases dramatically, increase the FF amount than the calculated FF amount,
The purpose of this system is to eliminate overshoot and undershoot in the shortest possible time by responding to the initial changes in flow rate.The system is configured to adjust the flow rate at an appropriate position in the flow path leading from the inlet channel through the heat exchanger to the outlet channel. A detector is provided in the inlet waterway, an inlet water temperature detector in the outlet path, and a proportional valve for controlling the combustion amount in the gas path to the burner that heats the heat exchanger. In a water heater equipped with a temperature setting device that sets the hot water temperature, a combustion amount calculation circuit that calculates and outputs the combustion amount from the flow rate, inlet water temperature, and set temperature, and a combustion amount calculation circuit that calculates and outputs the combustion amount from the flow rate, inlet water temperature, and set temperature, and a difference between the outlet hot water temperature and the set temperature or the heat exchanger outlet a proportional integral circuit that corrects the difference between the temperature and a set temperature of the heat exchanger; and a combustion amount correction circuit that combines the output of the combustion amount calculation circuit and the output of the proportional integration circuit to generate a proportional valve drive output. Further, a proportional integral amount correction circuit for correcting unnecessary proportional integral amount is provided between the proportional integral circuit and the combustion amount correction circuit, and a proportional integral amount correction circuit for correcting unnecessary proportional integral amount is provided between the flow rate detection circuit and the said proportional integral amount correction circuit, and a A combustion amount calculation circuit that adds, subtracts, multiplies, or subtracts a percentage of the flow rate change or a fixed percentage between the combustion amount calculation circuit and the combustion amount correction circuit. The change circuit is provided in a hot water control device having a timer circuit between the flow rate change detection circuit, the combustion amount calculation change circuit, and the proportional-integral amount correction circuit.

[0006]

[Operation] When using at a constant flow rate, inlet water temperature, and set temperature, the outputs of the outlet hot water temperature detector and temperature setting device are always compared by the proportional integral circuit, and the proportional integral is performed. The combustion amount correction amount is added to the output of , and the result is supplied to the combustion amount correction circuit. However, when the flow rate changes suddenly, the flow rate change detection circuit detects this and activates the proportional integral amount correction circuit, and the combustion amount calculation change circuit changes the output from the hot water temperature detection circuit, the flow rate change detection circuit, and the combustion amount calculation circuit. Based on the output, add a percentage of the flow rate change or a fixed percentage,
The combustion amount is calculated by subtraction, multiplication, or subtraction, and a control signal thereof is output to the combustion amount correction circuit, and the combustion amount correction circuit outputs a drive signal to the proportional valve. In this way, since the combustion amount is calculated by FF control, overshoot and undershoot are eliminated in a very short time, and the temperature of the hot water can be stabilized at an early stage. Then, if the tapped water temperature satisfies a certain condition, a control release signal is sent from the combustion amount calculation change circuit, or if a certain period of time has elapsed after the start of control, a control release signal is sent from the timer circuit to the combustion amount correction circuit via the combustion amount calculation change circuit. hand,
The hot water control system returns to normal control operation.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a water heater according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is an overall circuit diagram of an embodiment of the water heater of the present invention, in which an inlet water channel 2 connected to a heat exchanger 1 is provided with an inlet water amount detector 3 as a flow rate detector and an inlet water temperature detector 4, In addition, a hot water temperature detector 6 is provided in the hot water outlet path 5 from the heat exchanger 1, and a proportional valve 9 for controlling the amount of combustion is provided in the gas path 8 to the burner 7 that heats the heat exchanger 1. Furthermore, a temperature setting device 10 is provided for setting the temperature of hot water at the place where hot water is used or the temperature of hot water in the heat exchanger 1. A hot water temperature control device 11 is provided which inputs signals from the incoming water amount detector 3, incoming water temperature detector 4, and temperature setting device 10 and outputs a drive signal to the proportional valve 9. As a flow rate detector, a hot water output flow rate detector (not shown) can be provided in the hot water outlet path 5 instead of the water input flow rate detector 3, and can function in the same manner as the water input flow rate detector 3.

The hot water temperature control device 11 has a circuit configuration as shown in FIG. That is, a flow rate detection circuit 23 that detects signals from each of the incoming water amount detector 3, incoming water temperature detector 4, and outgoing hot water temperature detector 6, incoming water temperature detection circuit 24, outgoing hot water temperature detection circuit 26, and temperature setting. A temperature setting circuit 30 that detects and calculates a set temperature signal from the device 10 is provided, and a combustion amount calculation circuit that calculates and outputs a combustion amount from the output signals of the flow rate detection circuit 23, the incoming water temperature detection circuit 24, and the temperature setting circuit 30. 31, hot water temperature detection circuit 26, and temperature setting circuit 30
A proportional integral circuit 32 corrects the difference between the outlet hot water temperature and the set temperature or the difference between the outlet temperature of the heat exchanger 1 and the set temperature of the heat exchanger 1 from the output signal of the output of the combustion amount calculation circuit 31 and the set temperature of the heat exchanger 1. It includes a combustion amount correction circuit 33 that combines the output of the proportional integral circuit 32 and outputs a proportional valve drive output.

Furthermore, a proportional integral amount correction circuit 34 for correcting unnecessary proportional integral amount is provided between the proportional integral circuit 32 and the combustion amount correcting circuit 33, and a proportional integral amount correcting circuit 34 is provided between the flow rate detection circuit 23 and the proportional integral amount correcting circuit 34. A flow rate change detection circuit 35 that detects sudden changes in the amount of water entering is provided between the combustion amount calculation circuit 31 and the combustion amount correction circuit 33 by addition, subtraction, or multiplication by a proportion of the flow rate change or a fixed proportion. The combustion amount calculation change circuit 36 that performs subtraction is connected to the flow rate change detection circuit 35 and the combustion amount calculation change circuit 3.
6 and the proportional integral amount correction circuit 34.
It is equipped with

The water heater constructed as described above operates as follows. That is, when using the water at a constant amount, water temperature, and set temperature, the hot water output temperature detector 6 and the temperature setting device 10 are activated.
The output from the combustion amount calculation circuit 31 is constantly compared with the output from the combustion amount calculation circuit 31 to perform proportional integration, and the output from the combustion amount calculation circuit 31 is added with a combustion amount correction amount and is supplied to the combustion amount correction circuit 33. A drive signal is output to the proportional valve 9. However, when the amount of water entering suddenly changes, the flow rate change detection circuit 35 detects this and activates the proportional integral amount correction circuit 34 to set the proportional integral amount to 0, and the combustion amount calculation change circuit 36 changes the output hot water temperature detection circuit. 26. Based on the outputs from the flow rate change detection circuit 35 and the combustion amount calculation circuit 31, add, subtract, multiply, or subtract by the proportion of the flow rate change or a fixed proportion to calculate the combustion quantity. The control signal is output to the amount correction circuit 33, and the combustion amount correction circuit 33 outputs a drive signal to the proportional valve 9. Then, when the hot water temperature satisfies a certain condition, the control is released from the combustion amount calculation change circuit 36, or from the timer circuit 37, after a certain period of time has passed after the start of control, to the combustion amount correction circuit 33 via the combustion amount calculation change circuit 36. The signal is sent, and the hot water temperature control device 11 returns to normal control operation.

[0011] As described above, the combustion amount is calculated by FF control, but to explain in more detail an example of FF control when the flow rate changes, (1-1) Conditions for establishing (previous flow rate - current flow rate)> K1 (l/min) and after the cold start control is completed. However, K1: Constant 1 to 20 (1-2) Condition If the above conditions are met, the flow rate is rapidly decreased. (1-3) Control procedure in that state: Supply the FF amount calculated by the following equation. Ipt=IPF×K2 However, Ipt: amount of heat given IPF: calculated amount of FF heat K2: constant 0.1 to 1.0 (1-4) Conditions for canceling control now, en: current (hot water setting temperature - hot water temperature) )
en-1: If the previous (hot water setting temperature - hot water temperature), hot water setting temperature < hot water temperature, and (en-1
-en) changes from positive to negative, the hot water temperature < (hot water set temperature + 5) holds true, or T1 after the start of control.
Control is canceled when the time has elapsed. However, T1: 1 to 60 seconds

(2-1) Conditions to be met (previous flow rate - current flow rate) > K1 (l/min), and after cold start control is completed. However, K1: constant 1 to 20 (2-2) Conditions as described above If the conditions are met, the flow rate is rapidly increased. (2-3) Control procedure for that state: Supply the FF amount calculated by the following equation. Ipt=IPF×K3 However, Ipt: amount of heat given IPF: calculated amount of FF heat K3: constant 1.0 to 2.0 (2-4) Conditions for canceling control now, en: Current (hot water setting temperature - hot water exit temperature) )
en-1: If the previous (hot water setting temperature - hot water temperature), hot water setting temperature > hot water temperature, and (en-1
-en) changes from negative to positive, the hot water outlet temperature > (the hot water outlet set temperature -5) is established, or T2 after the start of the control
Control is canceled when the time has elapsed. However, T2: 1 to 60 seconds

[0013] In the FB control when the amount of water entering suddenly changes, the proportional-integral amount correction circuit 34 can perform either of the following two methods. (1) FB amount calculation is not updated. Ipt = IPF × (K2 or K3) + (current flow rate / previous flow rate) × IPB However, Ipt: amount of heat given IPF: calculated amount of FF heat IPB: calculated amount of FB heat, that is, IPB when the flow rate changes is the previous value Use as is. (2) Set the FB amount to 0.

As explained above, in the present invention, when the amount of water entering suddenly changes, the combustion amount is calculated by the FF control instead of the FB control in the combustion amount calculation change circuit 36, so that the conditions for canceling the control are By giving more or less FF amount than the FF amount of normal calculation,
Compared to the method of gradually increasing or decreasing the combustion amount by FB control, overshoot and undershoot can be eliminated in a much shorter time, and the temperature of the hot water can be stabilized earlier.

[0015]

As described above, the water heater according to the present invention includes a combustion amount calculation circuit, a proportional-integral circuit, and a combustion amount correction circuit, and also has a proportional-integral amount correction circuit and a flow rate change detection circuit. Furthermore, between the combustion amount calculation circuit and the combustion amount correction circuit, a combustion amount calculation change circuit that performs addition, subtraction, multiplication, or subtraction by a proportion of the flow rate change or a fixed proportion is provided. Since a hot water control device each having a timer circuit is provided between the change detection circuit and the combustion amount calculation change circuit, FB control is not performed when the flow rate changes suddenly.
When the flow rate drastically decreases, the FF amount is made smaller than the calculated FF amount, and when the flow rate increases, the FF amount is made larger than the calculated FF amount, and overshoots and undershoots are eliminated in the shortest possible time by responding from the beginning of the flow rate change. It enables early stabilization of the tap water temperature, and has great practical value.

[Brief explanation of the drawing]

FIG. 1 is an overall circuit diagram of an embodiment of a water heater according to the present invention.

FIG. 2 is a block diagram showing an embodiment of a water heater according to the present invention.

FIG. 3 is a block diagram showing a conventional example.

[Explanation of symbols]

1. Heat exchanger, 2. Inlet channel, 3. Incoming water amount detector,
4.Incoming water temperature detector, 5.Output water path, 6.Output hot water temperature detector, 7.Burner, 8.Gas path, 9.Proportional valve, 10
・・Temperature setting device, 11.・Hot water temperature control device. 23..Flow rate detection circuit, 24..Incoming water temperature detection circuit, 26..Output water temperature detection circuit, 30..Temperature setting circuit, 31..Combustion amount calculation circuit, 32..Proportional integral circuit, 33..Combustion amount correction circuit,
34: Proportional integral amount correction circuit, 35: Flow rate change detection circuit, 36: Combustion amount calculation change circuit, 37: Timer circuit.

Claims (1)

[Claims] 1. A flow rate detector is provided at an appropriate position in a flow path leading from the inlet channel to the outlet channel via the heat exchanger, an inlet water temperature detector is provided in the inlet channel, and an outlet water temperature detector is provided in the outlet channel; In a water heater, the gas path to the burner that heats the heat exchanger is provided with a proportional valve for controlling the amount of combustion, and a temperature setting device for setting the temperature of the hot water. a combustion amount calculation circuit that calculates and outputs the amount; a proportional integral circuit that corrects the difference between the outlet hot water temperature and the set temperature or the difference between the heat exchanger outlet temperature and the heat exchanger set temperature; and the output of the combustion amount calculation circuit. and a combustion amount correction circuit that combines the outputs of the and the proportional integral circuit to generate a proportional valve drive output,
Further, a proportional integral amount correction circuit for correcting unnecessary proportional integral amount is provided between the proportional integral circuit and the combustion amount correction circuit, and a proportional integral amount correction circuit for correcting unnecessary proportional integral amount is provided between the flow rate detection circuit and the said proportional integral amount correcting circuit. Furthermore, a combustion amount calculation change circuit is provided between the combustion amount calculation circuit and the combustion amount correction circuit to perform addition, subtraction, multiplication, or subtraction by a proportion of the flow rate change or a fixed proportion. A water heater, characterized in that a hot water control device having a timer circuit is provided between the flow rate change detection circuit, the combustion amount calculation change circuit, and the proportional-integral amount correction circuit.